Why Do Eye Doctors Use Dilation Drops?

If you have ever had a comprehensive eye examination, it is likely that you have heard about dilating eye drops. These drops are used in the eye examination to better evaluate the back of your eyes.

How Does Dilation Occur?

In optometry, the term dilation refers to the increase of the size of the pupil. The pupil is the black portion of the center of the eye and is actually a hole in the colored portion of the eye, the iris.

The iris contains muscles which can make the pupil smaller or larger to allow more or less light into the eyes.

The iris will dilate when there is less light around, such as in a dark room. You may notice that when you are in a dark room for a long time, your pupils will appear much larger than normal.

Conversely, the iris will constrict in bright conditions. When exposed to a very bright environment, such as being outside on a sunny day, the iris will cause the pupil to become very small and limit the amount of light being let into the eyes.

By changing the size of the pupil, the iris is able to ensure that the optimal amount of light is let into the eye.

How Do Eye Dilation Drops Work?

Dilating drops are eye drops which work on the iris to increase the size of the pupil and dilate the eyes.

These drops act on the nerves in the iris muscles to trigger an increase in dilation and a decrease in constriction.

By combining these two mechanisms, the dilating eye drops are able to increase the size of the pupil and maintain the larger pupil size even in bright conditions.

Common dilating eye drops are tropicamide and phenylephrine. Other drops can dilate the eyes but produce a much stronger affect for a longer time. These include atropine and cyclopentolate.

Why Do I Need My Eyes Dilated in an Eye Exam?

In an eye examination, one of the most important structures to evaluate is the retina in the back of the eye.

The retina is responsible for sensing light and processing visual input to be sent to the brain.

To examine this structure, an eye doctor can use a specialized light and high-powered lens to view the retina.

Since the light is very bright, it will naturally cause the pupil to constrict. Through a small pupil, the eye doctor can only evaluate a central portion of the retina.

However, if dilating drops are used and the pupil is dilated, the eye doctor can view and examine the entire retina to assess the health.

What are Side Effects of Dilating Eye Drops?